package framework.utils;

// skip32-java is an implementation of SKIP32 cipher written in Java. SKIP32 is a 80-bit key, 32-bit block cipher based on Skipjack. The original implementation is written by Greg Rose and can be found at https://opensource.qualcomm.com/assets/dotc/skip32.c
// use: https://github.com/boivie/skip32-java/blob/master/src/main/java/com/boivie/skip32/Skip32.java
// BSD-3-Clause license

import org.springframework.util.Assert;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;

public class Skip32Util {

    private static final int FTABLE[] = {0xa3, 0xd7, 0x09, 0x83, 0xf8, 0x48,
            0xf6, 0xf4, 0xb3, 0x21, 0x15, 0x78, 0x99, 0xb1, 0xaf, 0xf9, 0xe7,
            0x2d, 0x4d, 0x8a, 0xce, 0x4c, 0xca, 0x2e, 0x52, 0x95, 0xd9, 0x1e,
            0x4e, 0x38, 0x44, 0x28, 0x0a, 0xdf, 0x02, 0xa0, 0x17, 0xf1, 0x60,
            0x68, 0x12, 0xb7, 0x7a, 0xc3, 0xe9, 0xfa, 0x3d, 0x53, 0x96, 0x84,
            0x6b, 0xba, 0xf2, 0x63, 0x9a, 0x19, 0x7c, 0xae, 0xe5, 0xf5, 0xf7,
            0x16, 0x6a, 0xa2, 0x39, 0xb6, 0x7b, 0x0f, 0xc1, 0x93, 0x81, 0x1b,
            0xee, 0xb4, 0x1a, 0xea, 0xd0, 0x91, 0x2f, 0xb8, 0x55, 0xb9, 0xda,
            0x85, 0x3f, 0x41, 0xbf, 0xe0, 0x5a, 0x58, 0x80, 0x5f, 0x66, 0x0b,
            0xd8, 0x90, 0x35, 0xd5, 0xc0, 0xa7, 0x33, 0x06, 0x65, 0x69, 0x45,
            0x00, 0x94, 0x56, 0x6d, 0x98, 0x9b, 0x76, 0x97, 0xfc, 0xb2, 0xc2,
            0xb0, 0xfe, 0xdb, 0x20, 0xe1, 0xeb, 0xd6, 0xe4, 0xdd, 0x47, 0x4a,
            0x1d, 0x42, 0xed, 0x9e, 0x6e, 0x49, 0x3c, 0xcd, 0x43, 0x27, 0xd2,
            0x07, 0xd4, 0xde, 0xc7, 0x67, 0x18, 0x89, 0xcb, 0x30, 0x1f, 0x8d,
            0xc6, 0x8f, 0xaa, 0xc8, 0x74, 0xdc, 0xc9, 0x5d, 0x5c, 0x31, 0xa4,
            0x70, 0x88, 0x61, 0x2c, 0x9f, 0x0d, 0x2b, 0x87, 0x50, 0x82, 0x54,
            0x64, 0x26, 0x7d, 0x03, 0x40, 0x34, 0x4b, 0x1c, 0x73, 0xd1, 0xc4,
            0xfd, 0x3b, 0xcc, 0xfb, 0x7f, 0xab, 0xe6, 0x3e, 0x5b, 0xa5, 0xad,
            0x04, 0x23, 0x9c, 0x14, 0x51, 0x22, 0xf0, 0x29, 0x79, 0x71, 0x7e,
            0xff, 0x8c, 0x0e, 0xe2, 0x0c, 0xef, 0xbc, 0x72, 0x75, 0x6f, 0x37,
            0xa1, 0xec, 0xd3, 0x8e, 0x62, 0x8b, 0x86, 0x10, 0xe8, 0x08, 0x77,
            0x11, 0xbe, 0x92, 0x4f, 0x24, 0xc5, 0x32, 0x36, 0x9d, 0xcf, 0xf3,
            0xa6, 0xbb, 0xac, 0x5e, 0x6c, 0xa9, 0x13, 0x57, 0x25, 0xb5, 0xe3,
            0xbd, 0xa8, 0x3a, 0x01, 0x05, 0x59, 0x2a, 0x46};

    private static int g(byte[] key, int k, int w) {
        int g1, g2, g3, g4, g5, g6;

        g1 = w >> 8;
        g2 = w & 0xff;

        g3 = FTABLE[g2 ^ (key[(4 * k) % 10] & 0xFF)] ^ g1;
        g4 = FTABLE[g3 ^ (key[(4 * k + 1) % 10] & 0xFF)] ^ g2;
        g5 = FTABLE[g4 ^ (key[(4 * k + 2) % 10] & 0xFF)] ^ g3;
        g6 = FTABLE[g5 ^ (key[(4 * k + 3) % 10] & 0xFF)] ^ g4;

        return (g5 << 8) + g6;
    }

    /**
     * Applies the SKIP32 function on the provided value stored in buf and
     * modifies it inplace. This is a low-level function used by the encrypt and
     * decrypt functions.
     *
     * @param key
     * @param buf
     * @param encrypt
     */
    public static void skip32(byte[] key, int[] buf, boolean encrypt) {
        int k; /* round number */
        int i; /* round counter */
        int kstep;
        int wl, wr;

        /* sort out direction */
        if (encrypt) {
            kstep = 1;
            k = 0;
        } else {
            kstep = -1;
            k = 23;
        }

        /* pack into words */
        wl = (buf[0] << 8) + buf[1];
        wr = (buf[2] << 8) + buf[3];

        /* 24 feistel rounds, doubled up */
        for (i = 0; i < 24 / 2; ++i) {
            wr ^= g(key, k, wl) ^ k;
            k += kstep;
            wl ^= g(key, k, wr) ^ k;
            k += kstep;
        }

        /* implicitly swap halves while unpacking */
        buf[0] = (wr >> 8);
        buf[1] = (wr & 0xFF);
        buf[2] = (wl >> 8);
        buf[3] = (wl & 0xFF);
    }

    /**
     * Encrypts the provided value using the specified key
     * <p>
     * The key should be a byte array of 10 elements.
     *
     * @param value
     * @param key
     * @return The encrypted value
     */
    public static int encrypt(int value, byte[] key) {
        int[] buf = new int[4];
        buf[0] = ((value >> 24) & 0xff);
        buf[1] = ((value >> 16) & 0xff);
        buf[2] = ((value >> 8) & 0xff);
        buf[3] = ((value >> 0) & 0xff);

        skip32(key, buf, true);

        int out = ((buf[0]) << 24) | ((buf[1]) << 16) | ((buf[2]) << 8)
                | (buf[3]);

        return out;
    }

    /**
     * Decrypts the provided value using the specified key
     * <p>
     * The key should be a byte array of 10 elements.
     *
     * @param value
     * @param key
     * @return The decrypted value
     */
    public static int decrypt(int value, byte[] key) {
        int[] buf = new int[4];

        buf[0] = ((value >> 24) & 0xff);
        buf[1] = ((value >> 16) & 0xff);
        buf[2] = ((value >> 8) & 0xff);
        buf[3] = ((value >> 0) & 0xff);

        skip32(key, buf, false);

        int out = ((buf[0]) << 24) | ((buf[1]) << 16) | ((buf[2]) << 8)
                | (buf[3]);

        return out;
    }

    // 无位移方式提取后4字节
    private static int extractLast4Bytes(long value) {
        byte[] bytes = ByteBuffer.allocate(8)
                .order(ByteOrder.BIG_ENDIAN)
                .putLong(value)
                .array();
        return ByteBuffer.wrap(new byte[]{
                bytes[5], bytes[7],
                bytes[2], bytes[3]
        }).getInt();
    }

    // 组合高低位
    private static long combine(long original, int newLower32) {
        byte[] originalBytes = ByteBuffer.allocate(8)
                .order(ByteOrder.BIG_ENDIAN)
                .putLong(original)
                .array();
        byte[] newLowerBytes = ByteBuffer.allocate(4)
                .order(ByteOrder.BIG_ENDIAN)
                .putInt(newLower32)
                .array();
        // System.arraycopy(newLowerBytes, 0, originalBytes, 2, 4);
        originalBytes[5] = newLowerBytes[0];
        originalBytes[7] = newLowerBytes[1];
        originalBytes[2] = newLowerBytes[2];
        originalBytes[3] = newLowerBytes[3];
        return ByteBuffer.wrap(originalBytes)
                .getLong();
    }

    // 加密低32位
    public static long partEncrypt(long value, byte[] key) {
        int lower32 = extractLast4Bytes(value);
        int encrypted = encrypt(lower32, key);
        return combine(value, encrypted);
    }

    // 解密并ID
    public static long partDecrypt(long encrypted, byte[] key) {
        int lower32 = extractLast4Bytes(encrypted);
        int decrypted = decrypt(lower32, key);
        return combine(encrypted, decrypted);
    }

    public static void main(String[] args) {
        byte[] key = {0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x8, 0x9, 0xA};

        int original = 12345678;
        int encrypted = encrypt(original, key);
        int decrypted = decrypt(encrypted, key);

        System.out.println("Original: " + original);
        System.out.println("Encrypted: " + encrypted);
        System.out.println("Decrypted: " + decrypted);

        Assert.isTrue(original == decrypted, "Skip32 test failed");


        Long l, s, d;
        l = IdUtil.newId();
        s = partEncrypt(l, key);
        d = partDecrypt(s, key);
        System.out.printf("%d, %d, %d, %d, %d\n", l, l.toString().length(), s, s.toString().length(), d);
        Assert.isTrue(l.equals(d), "Skip32 encrypt failed");
        l = IdUtil.newId();
        s = partEncrypt(l, key);
        d = partDecrypt(s, key);
        System.out.printf("%d, %d, %d, %d, %d\n", l, l.toString().length(), s, s.toString().length(), d);
        Assert.isTrue(l.equals(d), "Skip32 encrypt failed");
        l = IdUtil.newId();
        s = partEncrypt(l, key);
        d = partDecrypt(s, key);
        System.out.printf("%d, %d, %d, %d, %d\n", l, l.toString().length(), s, s.toString().length(), d);
        Assert.isTrue(l.equals(d), "Skip32 encrypt failed");
        l = IdUtil.newId();
        s = partEncrypt(l, key);
        d = partDecrypt(s, key);
        System.out.printf("%d, %d, %d, %d, %d\n", l, l.toString().length(), s, s.toString().length(), d);
        Assert.isTrue(l.equals(d), "Skip32 encrypt failed");
        l = IdUtil.newId();
        s = partEncrypt(l, key);
        d = partDecrypt(s, key);
        System.out.printf("%d, %d, %d, %d, %d\n", l, l.toString().length(), s, s.toString().length(), d);
        Assert.isTrue(l.equals(d), "Skip32 encrypt failed");


    }
}
